Recently, thinning and miniaturization of a semiconductor device and its package have been increasingly demanded. Therefore, as the semiconductor device and its package, flip chip type semiconductor devices in which a semiconductor element such as a semiconductor chip is mounted (flip chip-connected) on a substrate by means of flip chip bonding have been widely utilized. In such flip chip connection, a semiconductor chip is fixed to a substrate in a form where a circuit face of the semiconductor chip is opposed to an electrode-formed face of the substrate. In such a semiconductor device or the like, there may be a case where the back surface of the semiconductor chip is protected with a protective film to prevent the semiconductor chip from damaging or the like (see, Patent Document 1 to 10).    Patent Document 1: JP-A-2008-166451    Patent Document 2: JP-A-2008-006386    Patent Document 3: JP-A-2007-261035    Patent Document 4: JP-A-2007-250970    Patent Document 5: JP-A-2007-158026    Patent Document 6: JP-A-2004-221169    Patent Document 7: JP-A-2004-214288    Patent Document 8: JP-A-2004-142430    Patent Document 9: JP-A-2004-072108    Patent Document 10: JP-A-2004-063551
However, the protection of the back surface of a semiconductor chip with a protective film requires an additional step of attaching the protective film to the back surface of the semiconductor chip obtained in a dicing step. As a result, the number of the processing steps increases and the production cost is thereby increased. Moreover, the recent tendency toward thinning may result in that semiconductor chips are sometimes damaged in the step of picking up the semiconductor chips. Accordingly, until the picking-up step inclusive, semiconductor wafers and semiconductor chips are required to be reinforced for the purpose of enhancing the mechanical strength thereof. In particular, the thinning of the semiconductor chips may generate warp on the semiconductor chips in some cases, so that suppression or prevention of the generation of the warp is required.
The present invention has been made in consideration of the foregoing problem and an object thereof is to provide a film for flip chip type semiconductor back surface capable of suppressing or preventing the generation of warp on a semiconductor element flip chip-connected on an adherend, and a dicing tape-integrated film for wafer back surface.
Moreover, another object of the invention is to provide a process for producing a semiconductor device capable of flip chip-connecting a semiconductor element on an adherend with suppressing the generation of warp and, as a result, capable of improving a production yield.
In order to solve the foregoing related-art problems, the present inventors made extensive and intensive investigations. As a result, it has been found that the generation of warp on the semiconductor flip chip-connected on an adherend can be reduced by containing a prescribed amount or more of an inorganic filler in a film for flip chip type semiconductor back surface, leading to accomplishment of the invention.
Namely, the present invention provides a film for flip chip type semiconductor back surface to be formed on a back surface of a semiconductor element flip chip-connected to an adherend, the film for flip chip type semiconductor back surface comprising an inorganic filler in an amount within a range of 70% by weight to 95% by weight based on the whole of the film for flip chip type semiconductor back surface.
In flip chip mounting, it is common that a molding resin for encapsulating the whole of a semiconductor package is not used and only a bump connecting part between the adherend and the semiconductor element is encapsulated with an encapsulating resin called underfill. Therefore, the back surface of the semiconductor element is naked. For example, at the time when the encapsulating resin is thermally cured, a stress is applied to the semiconductor element owing to the curing and contraction thereof and, resulting from the stress, warp may be generated on the semiconductor element in some cases. Particularly, in a thin semiconductor element having a thickness of 300 μm or less (further, a thickness of 200 μm or less), the generation of warp becomes remarkable.
The film for flip chip type semiconductor back surface of the invention exerts the function of protecting a semiconductor element flip chip-connected onto an adherend when the film is formed on a back surface of the semiconductor element. Moreover, in the film for flip chip type semiconductor back surface of the invention, since 70% by weight or more of an inorganic filler is contained based on the whole of the film for flip chip type semiconductor back surface, tensile storage modulus of the film is relatively high. As a result, the warp of the semiconductor element, which may be generated at the thermal curing of the encapsulating resin, can be effectively suppressed or prevented. Moreover, by controlling the content of the inorganic filler to 95% by weight or less, appropriate flexibility can be imparted to the film. Incidentally, the back surface of the semiconductor element means a surface opposite to the surface thereof on which a circuit is formed.
The film for flip chip type semiconductor back surface preferably has a thickness within a range of 2 μm to 200 μm. By controlling the thickness to 2 μm or more, the mechanical strength of the film can be improved and a good self-supporting property can be secured. On the other hand, by controlling the thickness to 200 μm or less, it becomes possible to thin a semiconductor device composed of the semiconductor element flip chip-mounted on the adherend.
The semiconductor element preferably has a thickness within a range of 20 μM to 300 μm.
The present invention also provides a dicing tape-integrated film for semiconductor back surface, comprising a dicing tape and the above-mentioned film for flip chip type semiconductor back surface laminated on the dicing tape, wherein the dicing tape comprises a base material and a pressure-sensitive adhesive layer laminated on the base material, and the film for flip chip type semiconductor back surface is laminated on the pressure-sensitive adhesive layer.
According to the dicing tape-integrated film for semiconductor back surface having the constitution as above, the dicing tape and the film for flip chip type semiconductor back surface are formed in an integrated form, and therefore, the dicing tape-integrated film for semiconductor back surface can also be provided for a dicing step of dicing a semiconductor wafer to prepare a semiconductor element or the subsequent picking-up step. Namely, when a dicing tape is attached to the back surface of a semiconductor wafer prior to the dicing step, the film for semiconductor back surface can also be attached thereto, and therefore, a step of attaching the film for semiconductor back surface alone (attaching step of the film for semiconductor back surface) is not required. As a result, the number of processing steps may be reduced. Additionally, since the film for semiconductor back surface protects the back surface of the semiconductor wafer and that of the semiconductor element formed by dicing, damaging of the semiconductor element can be reduced or prevented during the dicing step and the subsequent steps (e.g., picking-up step). As a result, the production yield of the flip chip type semiconductor device can be improved.
The present invention further provides a process for producing a semiconductor device using the above-mentioned dicing tape-integrated film for semiconductor back surface, the process comprising: attaching a semiconductor wafer onto the film for flip chip type semiconductor back surface of the dicing tape-integrated film for semiconductor back surface, dicing the semiconductor wafer to form a semiconductor element, peeling the semiconductor element from the pressure-sensitive adhesive layer of the dicing tape together with the film for flip chip type semiconductor back surface, and flip chip connecting the semiconductor element onto an adherend.
In the foregoing process, since the dicing tape-integrated film for semiconductor back surface is attached to the back surface of the semiconductor wafer, the step of attaching the film for semiconductor back surface alone (attaching step of the film for semiconductor back surface) is not required. Moreover, since the back surface of the semiconductor wafer and the semiconductor element is protected by the film for semiconductor back surface during the dicing of the semiconductor wafer and the picking-up of the semiconductor element formed by the dicing, damaging and the like can be prevented. As a result, the flip chip type semiconductor device can be produced with an improved production yield.
The foregoing step of flip chip connection (flip chip connecting) preferably comprises filling an encapsulating resin into a gap between the adherend and the semiconductor element flip chip-bonded on the adherend, followed by thermally curing the encapsulating resin.
At the time when the encapsulating resin is thermally cured, a stress is applied to the semiconductor element due to the curing and contraction thereof and, resulting from the stress, warp may be generated on the semiconductor element in some cases. Particularly, in a thin semiconductor element having a thickness of 300 μm or less (further, a thickness of 200 μm or less), the generation of warp becomes remarkable. However, in the foregoing process, since 70% by weight or more of an inorganic filler is contained based on the whole of the film for flip chip type semiconductor back surface, tensile storage modulus is relatively high. As a result, the warp of the semiconductor element, which may be generated at the thermal curing of the encapsulating resin, can be effectively suppressed or prevented.
The present invention furthermore provides a flip chip type semiconductor device, which is manufactured by the above-mentioned process.
According to the film for flip chip type semiconductor back surface of the invention, since the film is formed on the back surface of a semiconductor element flip chip-connected on an adherend, the film exerts the function of protecting the semiconductor element. Moreover, according to the film for flip chip type semiconductor back surface of the invention, since 70% by weight or more of an inorganic filler is contained based on the whole film for flip chip type semiconductor back surface, warp of the semiconductor element, which may be generated at flip chip connection of the semiconductor element on the adherend, can be effectively suppressed or prevented.
Moreover, according to the dicing tape-integrated film for semiconductor back surface of the invention, the dicing tape and the film for flip chip type semiconductor back surface are formed in an integrated form, and therefore, the dicing tape-integrated film for semiconductor back surface can also be provided for a dicing step of dicing a semiconductor wafer to prepare a semiconductor element or the subsequent picking-up step. As a result, a step of attaching the film for semiconductor back surface alone (attaching step of the film for semiconductor back surface) is not required. Furthermore, in the subsequent dicing step and pick-up step, since the film for semiconductor back surface is attached to the back surface of the semiconductor wafer or the back surface of the semiconductor element formed by dicing, the semiconductor wafer and the semiconductor element can be effectively protected and the damage of the semiconductor element can be suppressed or prevented. Moreover, at the time of flip chip-connection of the semiconductor element on the adherend, the generation of warp of the semiconductor element can be prevented.
Furthermore, according to the process for producing the semiconductor device of the invention, since the dicing tape-integrated film for semiconductor back surface is attached to the back surface of the semiconductor wafer and therefore, the step of attaching the film for semiconductor back surface alone is not required. Moreover, since the back surfaces of the semiconductor wafer and the semiconductor element are protected by the film for semiconductor back surface during the dicing of the semiconductor wafer and the picking-up of the semiconductor element formed by the dicing, damaging and the like can be prevented. Also, generation of warp on the semiconductor element can be prevented at the time when the semiconductor element is flip chip-connected onto the adherend. As a result, the flip chip type semiconductor device can be produced with improving the production yield.